Method of n-type doping carbon nanotube

ABSTRACT

A method of n-type doping a carbon nanotube includes the following steps: providing a single carbon nanotube; providing a film-like structure, wherein the film-like structure is a molybdenum disulfide film or a tungsten disulfide film; and converting at least one portion of the carbon nanotube from a p-type to an n-type by covering the carbon nanotube with the film-like structure.

FIELD

The present application relates to a method of n-type doping a carbonnanotube.

BACKGROUND

Carbon nanotubes have excellent mechanical and chemical properties, andhave a length of up to one micrometer and a diameter from severalnanometers to several tens of nanometers. Carbon nanotubes haveexcellent electrical conductivity and can be used in various electronicdevices, such as electric field reflection devices, optical switches inthe field of optical communications, and biological devices.

Methods for making carbon nanotubes include arc discharge, pulsed laservaporization, chemical vapor deposition, and so on. To use carbonnanotubes in a semiconductor device, such as a complementarymetal-oxide-semiconductor (CMOS) transistor, p-type and n-type MOStransistors are required. Therefore, a hole doping (p-type doping) or anelectron doping (n-doping) to carbon nanotubes is required.

Therefore, there is room for improvement in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 shows a schematic process flow of a method of n-type doping acarbon nanotube in a first embodiment according to the presentdisclosure.

FIG. 2 shows a schematic view of a portion of a single carbon nanotubecovered with a MoS₂ film or a WS₂ film in the first embodiment, whereinthe single carbon nanotube is in direct contact with the MoS₂ film orthe WS₂ film.

FIG. 3 shows a schematic view of entire single carbon nanotube coveredwith the MoS₂ film or the WS₂ film in the first embodiment, wherein thesingle carbon nanotube is in direct contact with the MoS₂ film or theWS₂ film.

FIG. 4 shows a schematic process flow of a method of n-type dopingcarbon nanotubes in a second embodiment according to the presentdisclosure.

FIG. 5 shows a schematic section view of a first carbon nanotubecomposite structure in a third embodiment according to the presentdisclosure.

FIG. 6 shows a schematic section view of a second carbon nanotubecomposite structure in the third embodiment.

FIG. 7 shows a schematic section view of a third carbon nanotubecomposite structure in the third embodiment.

FIG. 8 shows a schematic top view of a fourth carbon nanotube compositestructure in the third embodiment.

FIG. 9 shows a schematic top view of a fifth carbon nanotube compositestructure in the third embodiment.

FIG. 10 shows a schematic top view of a sixth carbon nanotube compositestructure in the third embodiment.

FIG. 11 shows a schematic section view of a back-gate tunnelingtransistor in a fourth embodiment according to the present disclosure.

FIG. 12 shows a three-dimensional schematic view of the back-gatetunneling transistor in the fourth embodiment.

FIG. 13 shows a current scan view of the back-gate tunneling transistorin logarithmic form in the fourth embodiment.

FIG. 14 shows a transfer characteristic curve of the back-gate tunnelingtransistor in the fourth embodiment.

FIG. 15 shows a typical output characteristic curve of the back-gatetunneling transistor in a BTBT operating mode in the fourth embodiment.

FIG. 16 shows a typical output characteristic curve of the back-gatetunneling transistor in a p-n junction operating mode in the fourthembodiment.

FIG. 17 shows a typical output characteristic curve of the back-gatetunneling transistor in the n-n junction operating mode in the fourthembodiment.

FIG. 18 shows transfer characteristic curves of the back-gate tunnelingtransistor and a carbon nanotube transistor in the fourth embodiment.

FIG. 19 shows a photocurrent view of the back-gate tunneling transistorin the fourth embodiment.

FIG. 20 shows an energy band view of a semiconducting carbon nanotube inthe back-gate tunneling transistor before the semiconducting carbonnanotube is in direct contact with the MoS₂ film.

FIG. 21 shows an energy band view of the semiconducting carbon nanotubein the back-gate tunneling transistor after the semiconducting carbonnanotube is in direct contact with the MoS₂ film.

FIG. 22 shows transfer characteristic curves of the back-gate tunnelingtransistor at different temperatures.

FIG. 23 shows sub-threshold swings in a diffusion area and a BTBT areaextracted from FIG. 22 .

FIG. 24 shows a typical output curve of the CNT-MoS₂ heterostructure inthe back-gate tunneling transistor under different gate voltages in theBTBT operating mode, wherein the typical output curve is drawn on asemi-logarithmic scale.

FIG. 25 shows an energy band view of a reverse rectifier diode inreverse bias.

FIG. 26 shows an energy band view of a Zener diode under reverse bias.

FIG. 27 shows the temperature-dependent output curves in a BTBT statewhen Vg=20V.

FIG. 28 shows inverse slopes of the band-to-band tunneling current (BTBTcurrent) versus temperature when Vg=20V.

FIG. 29 shows mapping view of source electrode and drain electrodecurrent I& at a temperature of 130K.

FIG. 30 shows transfer characteristic curves of a pure metallic carbonnanotube field effect transistor and a metallic carbon nanotube fieldeffect transistor having the MoS₂ film.

FIG. 31 shows a schematic view of a top-gate tunneling transistor in afifth embodiment according to the present disclosure.

FIG. 32 shows a schematic process flow of a method of p-type doping acarbon nanotube in a sixth embodiment according to the presentdisclosure.

FIG. 33 shows a schematic view of a tungsten diselenide (WSe₂) film or ablack phosphorus (BP) film covering and being in direct contact with aportion of a single carbon nanotube in the sixth embodiment.

FIG. 34 shows a schematic view of the tungsten diselenide (WSe₂) film orthe black phosphorus (BP) film covering and being in direct contact withentire single carbon nanotube in the sixth embodiment.

FIG. 35 shows transfer characteristic curves of a carbon nanotube fieldeffect transistor having the WSe₂ film and a pure carbon nanotube fieldeffect transistor.

FIG. 36 shows a schematic process flow of a method of p-type dopingcarbon nanotubes in a seventh embodiment according to the presentdisclosure.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

The term “outside” refers to a region that is beyond the outermostconfines of a physical object. The term “inside” indicates that at leasta portion of a region is partially contained within a boundary formed bythe object. The term “substantially” is defined to essentiallyconforming to the particular dimension, shape or other word thatsubstantially modifies, such that the component need not be exact. Forexample, substantially cylindrical means that the object resembles acylinder, but can have one or more deviations from a true cylinder. Theterm “comprising” means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to FIG. 1 , a method of n-type doping a carbon nanotube 12 ina first embodiment is provided, and the method includes the followingsteps:

S11, providing a single carbon nanotube 12;

S12, providing a film-like structure 14, wherein the film-like structure14 is a molybdenum disulfide (MoS₂) film or a tungsten disulfide (WS₂)film; and

S13: making at least one portion of the single carbon nanotube 12 indirect contact with the film-like structure 14.

During step S1, the carbon nanotube 12 has a one-dimensional tubularstructure. The carbon nanotube 12 can be a metallic carbon nanotube or asemiconducting carbon nanotube. The carbon nanotube 12 can be asingle-wall carbon nanotube, a double-wall carbon nanotube, and amulti-wall carbon nanotube. The diameter and length of the single carbonnanotube 12 are not limited. The length of the carbon nanotube 12 can begreater than 50 microns. The diameter of the single-walled carbonnanotube is in a range from 0.5 nanometers to 50 nanometers, thediameter of the double-walled carbon nanotube is in a range from 1.0nanometer to 50 nanometers, and the diameter of the multi-walled carbonnanotube is in a range from 1.5 nanometers to 50 nanometers. In oneembodiment, the carbon nanotube 12 is the single-walled carbon nanotubeor the double-walled carbon nanotube.

During step S12, the molybdenum disulfide (MoS₂) film and the tungstendisulfide (WS₂) film are both two-dimensional film-like structures 14.The material of the MoS₂ film is MoS₂, and the material of the WS₂ filmis WS₂. The thickness of the molybdenum disulfide (MoS₂) film and thetungsten disulfide (WS₂) film is not limited.

In one embodiment, the film-like structure 14 is the molybdenumdisulfide (MoS₂) film, and the thickness of the MoS₂ film is about 4.2nm (nanometers). In one embodiment, the thickness of the MoS₂ film is4.2 nm.

During step S13, the carbon nanotube 12 can be completely covered by theMoS₂ film or the WS₂ film, or can be partially covered by the MoS₂ filmor the WS₂ film.

The MoS₂ film or the WS₂ film can cover and directly contact with aportion of the single carbon nanotube 12, while the rest of the singlecarbon nanotube 12 is not covered and is not directly contacted with theMoS₂ film or the WS₂ film. The MoS₂ film or the WS₂ film can also coverand directly contact with entire single carbon nanotube 12. All portionsof the carbon nanotubes covered by the MoS₂ film or the WS₂ film are indirect contact with the MoS₂ film or the WS₂ film. As shown in FIG. 2 ,the MoS₂ film or the WS₂ film covers and is in direct contact with aportion of the single carbon nanotube 12. As shown in FIG. 3 , the MoS₂film or the WS₂ film covers and is in direct contact with the entireupper surface of the single carbon nanotube 12.

The portion of the single carbon nanotube 12 that is in direct contactwith the MoS₂ film or the WS₂ film is defined as a contact portion, andthe portion of the single carbon nanotube 12 that is not in directcontact with the MoS₂ film or the WS₂ film is defined as an exposedportion. The single carbon nanotube 12 consists of the contact portionand the exposed portion.

The carbon nanotube 12 is naturally a p-type semiconductor, and thecontact portion of the single carbon nanotube 12 is changed from p-typedoping to n-type doping. The reason is that the MoS₂ film or the WS₂film is in direct contact with the contact portion, MoS₂ or WS₂contributes electrons to the contact portion, electrons enter thecontact portion from MoS₂ or WS₂. The exposed portion of the singlecarbon nanotube 12 is still p-type, because the MoS₂ film or the WS₂film does not directly contact with the exposed portion, and the MoS₂ orWS₂ does not contribute electrons to the exposed portion and electronscannot enter the exposed portion from MoS₂ or WS₂.

Referring to FIG. 4 , a method of n-type doping carbon nanotubes in asecond embodiment is provided, and the method includes the followingsteps:

S21, providing a plurality of single carbon nanotubes 12 spaced apartfrom each other;

S22, providing the film-like structure 14, wherein the film-likestructure 14 is the molybdenum disulfide (MoS₂) film or the tungstendisulfide (WS₂) film; and

S23, covering the plurality of single carbon nanotubes 12 with the MoS₂film or the WS₂ film, wherein at least one portion of each of theplurality of single carbon nanotubes 12 is in direct contact with theMoS₂ film or the WS₂ film.

The method of n-type doping carbon nanotubes 12 in the second embodimentis similar to the method of n-type doping the carbon nanotube 12 in thefirst embodiment except that: in the first embodiment, the MoS₂ film orthe WS₂ film covers at least one portion of one single carbon nanotube12; in the second embodiment, the MoS₂ film or the WS₂ filmsimultaneously covers multiple single carbon nanotubes 12, and at leastone portion of each single carbon nanotube 12 is coved by the MoS₂ filmor the WS₂ film.

During step S21, the length extending directions of the plurality ofsingle carbon nanotubes 12 are parallel to each other.

During step S23, the MoS₂ film or the WS₂ film simultaneously cover aportion of each single carbon nanotubes 12, so that a portion of eachsingle carbon nanotube 12 is changed into the n-type from p-type. TheMoS₂ film or the WS₂ film covers all of the single carbon nanotubes 12at the same time, so that all of the single carbon nanotubes 12 aresimultaneously changed into the n-type from p-type.

The n-type doping methods for carbon nanotubes 12 in the first andsecond embodiments have the following advantages: first, the MoS₂ filmor the WS₂ film is in direct contact with a portion of the single carbonnanotube 12, which can change this portion from p-type doped to n-typedoped, thereby realizing n-type doping to the single carbon nanotube 12;second, one portion of the single carbon nanotube 12 is p-type and theother portion of the single carbon nanotube 12 is n-type, thus thesingle carbon nanotube 12 simultaneously contains p-type and n-type;third, simultaneously n-doping to multiple single carbon nanotubes 12can be performed; fourth, the n-doping method is simple, and the n-typedoping effect is good.

A carbon nanotube composite structure in the third embodiment isprovided, and the carbon nanotube composite structure is prepared by themethods in the first embodiment and the second embodiment.

Referring to FIG. 5 to FIG. 10 , the first carbon nanotube compositestructure 10 to the sixth carbon nanotube composite structure 60 aretook as examples to specifically describe the carbon nanotube compositestructure, but it is not limited by these. The carbon nanotube compositestructure 10, 20, 30, 40, 50, or 60 includes at least one single carbonnanotube 12 and at least one film-like structure 14, and the film-likestructure 14 is the MoS₂ film or the WS₂ film.

When the number of the single carbon nanotube 12 is one, the film-likestructure 14 is located on the outer surface of the single carbonnanotube 12 and is in direct contact with a portion of the single carbonnanotube 12. One portion of the single carbon nanotube 12 is in directcontact with the film-like structure 14, and not the entire outersurface of the single carbon nanotube 12 is in direct contact with thefilm-like structure 14.

When the number of the single carbon nanotubes 12 is multiple, themultiple single carbon nanotubes 12 are arranged at intervals. At leastone film-like structure 14 is located on the outer surface of the atleast one single carbon nanotube 12, and in direct contact with aportion of each single carbon nanotube 12. In one embodiment, the lengthextending directions of the plurality of single carbon nanotubes 12 arespaced apart from each other and parallel to each other. A portion ofeach single carbon nanotube 12 is in direct contact with the film-likestructure 14, and not all the outer surface of each single carbonnanotube 12 is in direct contact with the film-like structure 14.

The single carbon nanotube 12 includes at least one p-type portion andat least one n-type portion, and the p-type portion and the n-typeportion are alternately arranged. The p-type portion is the exposedportion, and the n-type portion is the contact portion.

The single carbon nanotube 12 simultaneously contains p-type and n-type.The film-like structure 14 is placed on the single carbon nanotube 12,and the film-like structure 14 is in direct contact with the n-typeportion. Furthermore, the outer surfaces of all of the n-type portionsare in direct contact with the film-like structure 14. In oneembodiment, the single carbon nanotube 12 consists of at least onep-type portion and at least one n-type portion alternately arranged, thefilm-like structure 14 is only located on the n-type portions and indirect contact with the n-type portions.

As shown in FIG. 5 , the first carbon nanotube composite structure 10consists of one single carbon nanotube 12 and one film-like structure14. The single carbon nanotube 12 consists of one p-type portion and onen-type portion. The film-like structure 14 covers the n-type portion andis in direct contact with the outer surface of the n-type portion.

As shown in FIG. 6 , the second carbon nanotube composite structure 20consists of one single carbon nanotube 12 and one film-like structure14. The single carbon nanotube 12 consists of a first p-type portion, asecond p-type portion, and an n-type portion; and the n-type portion isbetween the first p-type portion and the second p-type portion. Thesingle carbon nanotube 12 is a p-n-p type carbon nanotube. The film-likestructure 14 covers the n-type portion and is in direct contact with theouter surface of the n-type portion.

As shown in FIG. 7 , the third carbon nanotube composite structure 30consists of one single carbon nanotube 12 and two film-like structures14. The single carbon nanotube 12 consists of a first n-type portion, asecond n-type portion, and a p-type portion; and the p-type portion isbetween the first n-type portion and the second n-type portion. Thesingle carbon nanotube 12 is an n-p-n type carbon nanotube. Onefilm-like structure 14 covers the first n-type portion and is in directcontact with the outer surface of the first n-type portion, and theother film-like structure 14 covers the second n-type portion and is incontact with the outer surface the second n-type portion.

As shown in FIG. 8 , the fourth carbon nanotube composite structure 40consists of a plurality of single carbon nanotubes 12 and one film-likestructure 14. The plurality of single carbon nanotubes 12 is parallel toeach other and spaced apart from each other. Each single carbon nanotube12 consists of one p-type portion and one n-type portion. The film-likestructure 14 simultaneously covers the n-type portions of the pluralityof single carbon nanotubes 12 and is in direct contact with the outersurfaces of the n-type portions.

As shown in FIG. 9 , the fifth carbon nanotube composite structure 50consists of a plurality of single carbon nanotubes 12 and one film-likestructure 14. The plurality of single carbon nanotubes 12 is parallel toeach other and spaced apart from each other. Each single carbon nanotube12 consists of a first p-type portion, a second p-type portion, and ann-type portion; and the n-type portion is between the first p-typeportion and the second p-type portion. Each single carbon nanotube 12 isa p-n-p type carbon nanotube. The film-like structure 14 simultaneouslycovers the n-type portions of the plurality of single carbon nanotubes12 and is in direct contact with the outer surfaces of the n-typeportions.

As shown in FIG. 10 , the sixth carbon nanotube composite structure 60consists of a plurality of single carbon nanotubes 12 and two film-likestructures 14. The plurality of single carbon nanotubes 12 is parallelto each other and spaced apart from each other. Each single carbonnanotube 12 consists of a first n-type portion, a second n-type portionand a p-type portion; and the p-type portion is between the first n-typeportion and the second n-type portion. Each single carbon nanotube 12 isan n-p-n type carbon nanotube. One film-like structure 14 simultaneouslycovers the first n-type portions of the plurality of single carbonnanotubes 12 and is in direct contact with the outer surfaces of thefirst n-type portions, and the other film-like structure 14simultaneously covers the second n-type portions of the plurality ofsingle carbon nanotubes 12 and is in direct contact with the outersurfaces of the second n-type portions.

Furthermore, the single carbon nanotube 12 in the carbon nanotubecomposite structure may also be of various types, such as n-p-n-p type,p-n-p-n type, and so on.

No matter how many n-type portion are in the single carbon nanotube 12,the outer surfaces of all the n-type portions are in direct contact withthe film-like structure 14

It can be understood that the first carbon nanotube composite structure10, the second carbon nanotube composite structure 20, and the thirdcarbon nanotube composite structure 30 are prepared by the method in thefirst embodiment. The fourth carbon nanotube composite structure 40, thefifth carbon nanotube composite structure 50, and the sixth carbonnanotube composite structure 60 are prepared by the method in the secondembodiment.

The carbon nanotube composite structure, such as the first carbonnanotube composite structure 10 to the sixth carbon nanotube compositestructure 60, in the third embodiment has the following advantages:first, a portion of the single carbon nanotube 12 is p-type, and theother portion is n-type, and the single carbon nanotube 12 can consistof p-type and n-type; second, the single carbon nanotube 12 can ben-p-n, p-n-p, n-p-n-p, p-n-p-n, and other types; third, because thesingle carbon nanotube 12 contains p type and n-type, when the singlecarbon nanotube 12 is a semiconducting carbon nanotube, electrons cantunnel from the p-type valence band to the n-type conduction band, sothat the band to band tunneling (BTBT) can be performed.

Referring to FIG. 11 , a back-gate tunneling transistor 100 in a fourthembodiment is provided. The back-gate tunneling transistor 100 includesa single carbon nanotube 12, a film-like structure 14, a sourceelectrode 108, a drain electrode 109, an insulating layer 106, and agate 104. The back-gate tunneling transistor 100 can be formed on asurface of an insulating substrate 102. The single carbon nanotube 12 isa semiconducting carbon nanotube. The film-like structure 14 is amolybdenum disulfide (MoS₂) film or a tungsten disulfide (WS₂) film, thematerial of the MoS₂ film is MoS₂, and the material of the WS₂ film isWS₂. In one embodiment, the back-gate tunneling transistor 100 consistsof one single carbon nanotube 12, the film-like structure 14, the sourceelectrode 108, the drain electrode 109, the insulating layer 106, andthe gate 104.

The gate 104 is located on the surface of the insulating substrate 102,the insulating layer 106 is located on the surface of the gate 104 awayfrom the insulating substrate 102, and the single carbon nanotube 12 islocated on the surface of the insulating layer 106 away from the gate104. The film-like structure 14 covers and is in direct contact with aportion of the single carbon nanotube 12, and the single carbon nanotube12 is located between the insulating layer 106 and the film-likestructure 14. The source electrode 108 is electrically connected to thefilm-like structure 14, and the drain electrode 109 is electricallyconnected to the single carbon nanotube 12. The insulating layer 106 islocated between the source electrode 108 and the gate 104, and theinsulating layer 106 is also located between the drain electrode 109 andthe gate 104. In one embodiment, the source electrode 108 is in directcontact with the film-like structure 14, and the drain electrode 109 isin direct contact with the single carbon nanotube 12. Since the singlecarbon nanotube 12 is only one carbon nanotube and is one-dimensional,the film-like structure 14 is two-dimensional, a portion of thefilm-like structure 14 is in direct contact with the single carbonnanotube 12, and a portion of the film-like structure 14 is in directcontact with the insulating layer 106. A portion of the single carbonnanotube 12 is located between the film-like structure 14 and theinsulating layer 106, and this portion is in direct contact with boththe film-like structure 14 and the insulating layer 106.

The insulating substrate 102 plays a supporting role, and the materialof the insulating substrate 102 can be selected from hard materials suchas glass, quartz, ceramics, diamond, silicon wafers, or flexiblematerials such as plastics and resins. In one embodiment, the materialof the insulating substrate 102 is glass. The insulating substrate 102can also be a substrate in a large-scale integrated circuit, and aplurality of back-gate tunneling transistors 100 can be integrated onthe same insulating substrate 102 according to a predetermined rule orpattern.

The insulating layer 106 has an atomic level flat surface, and thematerial of the insulating layer 106 is boron nitride or the like. Thethickness of the insulating layer 106 can be in a range from about 5nanometers to about 100 microns. In one embodiment, the thickness of theinsulating layer 106 is in a range from 5 nanometers to 100 microns, thematerial of the insulating layer 106 is hexagonal boron nitride; and theinsulating layer 106 formed by the hexagonal boron nitride has an atomiclevel flat surface, the height difference between the highest place ofthe atomic level flat surface and the lowest place of the atomic levelflat surface is atomic-scale, and the height difference between thehighest place of the atomic level flat surface and the lowest place ofthe atomic level flat surface ranges in 1 atomic layer to 2 atomiclayers.

The materials of the source electrode 108 and the drain electrode 109should have good conductivity. The materials of the source electrode 108and the drain electrode 109 can be metal, alloy, indium tin oxide (ITO),antimony tin oxide (ATO), conductive silver paste, conductive polymer,metallic carbon nanotube film, and so on. The thickness of each of thesource electrode 108 and the drain electrode 109 can be in a range from0.5 nanometers to 100 micrometers. In one embodiment, the sourceelectrode 108 is an Au/Ti (gold/titanium, thickness is 50 nm/5 nm)electrode, and the Au/Ti electrode is formed by stacking a 50 nm thickgold layer and a 5 nm thick titanium layer; the 5 nm thick titaniumlayer is in direct contact with the film-like structure 14, the 50 nmthick Au layer is located on the surface of the titanium layer away fromthe film-like structure 14; and the material of the drain electrode 109is palladium (Pd), and the thickness of the drain electrode 109 is 50nm.

The material of the gate 104 has good conductivity. The material of thegate 104 can be conductive materials such as metal, alloy, ITO, ATO,conductive silver glue, conductive polymer, or carbon nanotube film. Themetal or alloy material can be aluminum, copper, tungsten, molybdenum,gold or their alloys. The thickness of the gate 104 is in a range fromabout 0.5 nanometers to about 100 microns. In one embodiment, thethickness of the gate 104 is in a range from 0.5 nanometers to 100microns, and the gate 104 is highly doped silicon.

A specific embodiment below is used to further illustrate the presentapplication, but it should not be a limitation to the presentapplication.

A highly doped silicon wafer (silicon is highly doped, thus the highlydoped silicon is conductive and as the gate 104) has a 300 nm thickoxide layer (the material of the oxide layer is SiO₂). A hexagonal boronnitride (hBN) sheet (as the insulating layer 106) is transferred to theoxide layer by a transparent tape, the hBN sheet is in direct contactwith the oxide layer, and the oxide layer is located between the highlydoped silicon wafer and the hBN sheet. Since the hBN sheet has an atomiclevel flat surface, and the atomic level flat surface has no danglingbonds, the hBN sheet can shield charge doping from the SiO₂. The innershell of a suspended semiconducting carbon nanotube is pulled out, andthen the semiconducting carbon nanotube is placed on the hBN sheet bytwo tungsten tips. Only semiconducting carbon nanotubes are selectedthrough electrical measurement. Since the inner shell of thesemiconducting carbon nanotube is pulled out, the semiconducting carbonnanotube is a single-wall carbon nanotube or a double-wall carbonnanotube.

Under an optical microscope with a micromanipulator, a piece of MoS₂film is placed on the semiconducting carbon nanotube, and the MoS₂ filmcovers only a portion of the semiconducting carbon nanotube. By usingstandard processes including electron beam lithography (EBL), electronbeam evaporation and stripping, Pd (palladium, thickness is 50 nm) andAu/Ti (gold/titanium, 50 nm/5 nm) electrode are used to respectivelyconnect to the semiconducting carbon nanotube and the MoS₂ film. Pd iselectrically connected to the semiconducting carbon nanotube and servesas the drain electrode 109. The Au/Ti electrode is electricallyconnected to the MoS₂ film and serves as the source electrode 108. Thesemiconducting carbon nanotube serves as a channel layer. In this way,the preparation of the back-gate tunneling transistor 100 is completed,as shown in FIG. 12 .

FIG. 12 shows a schematic view of the back-gate tunneling transistor 100and an additional measurement circuit diagram. The main body is amixed-dimensional heterojunction constructed or formed by thesemiconducting carbon nanotube and the molybdenum disulfide, metalpalladium is used as the contact electrode of the semiconducting carbonnanotube, and the Au/Ti electrode (the thickness of the Au is 50 nm, andthe thickness of the Ti is 5 nm) as the contact electrode of molybdenumdisulfide, to realize good p-type contact and n-type contactrespectively. In FIG. 12 , the two electrodes being in direct contactwith molybdenum disulfide are all titanium-gold electrodes (Au/Tielectrode), and the three electrodes being in direct contact with thesemiconducting carbon nanotubes are all palladium electrodes. It can beunderstood that, in FIG. 12 , only one titanium-gold electrode (Au/Tielectrode) can be in direct contact with or electrically connected tomolybdenum disulfide, and only a palladium electrode can be in directcontact with or electrically connected to the semiconducting carbonnanotubes. In the test, the heavily doped silicon substrate is the gate104, the semiconducting carbon nanotube is in direct contact with thedrain electrode 109, and the molybdenum disulfide is in direct contactwith the source electrode 108.

The working principle of the back-gate tunneling transistor 100 is: theMoS₂ film or the WS₂ film covers and is in direct contact with a portionof the semiconducting carbon nanotube, and a portion of thesemiconducting carbon nanotube directly contacting with the MoS₂ film orthe WS₂ film is changed from p-type doping to n-type doping, so that oneportion of the semiconducting carbon nanotube is p-type and the otherportion of the semiconducting carbon nanotube is n-type. Therefore, thesemiconducting carbon nanotube can form a p-n junction. Under a specificgate voltage, carriers can tunnel from the valence band of p-type carbonnanotube to the conduction band of n-type carbon nanotube, so thatcarriers can be transported from the drain electrode 109 to the sourceelectrode 108 by the band-to-band tunneling. The gate 104 controls thetunneling current by controlling the number of carriers in thesemiconducting carbon nanotube and MoS₂, so as to realize the switchconversion of the back-gate tunneling transistor 100.

FIGS. 13-29 are various performance characterizations of the back-gatetunneling transistor 100 of FIG. 12 . In FIGS. 13-29 , “CNT” representsthe semiconducting carbon nanotube, “CNT with MoS₂” represents thesemiconducting carbon nanotube whose middle portion is covered by theMoS₂ film (the middle portion of the semiconducting carbon nanotubecovered by the MoS₂ film is the contact portion), “Before contact”represents the semiconducting carbon nanotube before directly contactingwith the MoS₂ film, “After contact” represents the semiconducting carbonnanotube after directly contacting with the MoS₂ film, “overlappedregion” represents the overlapping region of the MoS₂ film and thesemiconducting carbon nanotube that is in direct contact with the MoS₂film, “BTBT region” represents the inter-band tunneling region where theinter-band tunneling mechanism dominates the carrier transport withinthe corresponding gate voltage range, “Diffusion region” represents theregion where the thermal diffusion mechanism dominates the carriertransport and diffusion within the corresponding gate voltage range, and“BTBT current” represents the band-to-band tunneling current.

FIG. 13 shows a current scan diagram of the back-gate tunnelingtransistor 100 in logarithmic form. In FIG. 13 , the horizontal axis isthe gate voltage (voltage of the gate 104), and the vertical axis is thesource electrode-drain electrode bias voltage; the two dashed linesdemarcate the operating modes of the back-gate tunneling transistor 100under different gate voltages; from right to left are the nn junctionarea, the pn junction area, and the BTBT area. FIG. 14 shows a transfercharacteristic curve of the back-gate tunneling transistor 100.

FIG. 15 shows a typical output characteristic curve of the back-gatetunneling transistor 100 in the BTBT operating mode. It can be seen fromFIG. 15 that the reverse current is greater than the forward current.FIG. 16 shows a typical output characteristic curve of the back-gatetunneling transistor 100 in the pn junction operation mode, and FIG. 16presents obvious forward rectification characteristics. FIG. 17 shows atypical output characteristic curve of the back-gate tunnelingtransistor 100 in the nn junction operation mode, and FIG. 17 presentspositive and anti-symmetric output characteristics.

The pn junction working mode and the nn junction working mode refer todifferent working modes under the adjustment of the gate voltage. Thegate voltage range corresponding to the nn junction working mode isapproximately +35˜+45V, the gate voltage range corresponding to the pnjunction working mode is approximately +20V˜+35V, and the gate voltagerange corresponding to the BTBT working mode is approximately −20V˜+20V.

FIG. 18 shows a transfer characteristic curve of the back-gate tunnelingtransistor 100 and a transfer characteristic curve of a carbon nanotubetransistor, wherein in the back-gate tunneling transistor 100, the MoS₂film covers the middle portion of the semiconducting carbon nanotube.The only difference between the carbon nanotube transistor and theback-gate tunneling transistor 100 is that the carbon nanotubetransistor does not contain the MoS₂ film, and the semiconducting carbonnanotubes are not covered by the MoS₂ film; and the back-gate tunnelingtransistor 100 contains the MoS₂ film, and the middle portion of thesemiconducting carbon nanotube is covered by MoS₂ film.

It can be seen from FIG. 18 that the back-gate tunneling transistor 100and the carbon nanotube transistor have a common switch off point at˜+35V (volt), and the transfer characteristic curve of the back-gatetunneling transistor 100 has an additional switch off point near −5V,which proves that the doping levels of the portion of the semiconductingcarbon nanotubes covered by the MoS₂ film (that is, the contact portion)and the portion of the semiconducting carbon nanotubes not covered byMoS₂ film (that is, the exposed portion) are different.

Before the single carbon nanotube 12 is in contact with the MoS₂ film,the single carbon nanotube 12 is a one-dimensional p-type channel, theMoS₂ film is a two-dimensional n-type channel, and the Fermi energylevel of the MoS₂ film is higher than that of the single carbon nanotube12 that is not in direct contact with the MoS₂ film. When the singlecarbon nanotube 12 is in direct contact with the MoS₂ film, electronscan be spontaneously transferred from the MoS₂ film to the single carbonnanotube 12 until the Fermi energy levels of the single carbon nanotube12 and the MoS₂ film are equal. Since electrons are spontaneouslytransferred from the MoS₂ film to the portion of the semiconductingcarbon nanotubes being in direct contact with the MoS₂ film, the portionof the semiconducting carbon nanotube being in direct contact with theMoS₂ film is converted from p-type doping to n-type doping, and theportion of semiconducting carbon nanotubes that is not in direct contactwith the MoS₂ film is still p-type.

FIG. 19 is a photocurrent diagram of the back-gate tunneling transistor100. FIG. 19 reflects that in the overlapping area between the MoS₂ filmand the semiconducting carbon nanotube, the direction of the built-inelectric field is from the MoS₂ film to the semiconducting carbonnanotube, which proves that electrons spontaneously transfer from theMoS₂ film to the semiconducting carbon nanotube.

FIG. 20 shows an energy band view of the semiconducting carbon nanotubein the back-gate tunneling transistor before the semiconducting carbonnanotube is in direct contact with the MoS₂ film. FIG. 21 shows anenergy band view of the semiconducting carbon nanotube in the back-gatetunneling transistor after the semiconducting carbon nanotube is indirect contact with the MoS₂ film. It can be seen from FIG. 21 that inthe overlapping area between the MoS₂ film and the semiconducting carbonnanotube, the semiconducting carbon nanotube is changed from p-typedoping to n-type doping.

FIG. 22 shows the transfer characteristic curves of the back-gatetunneling transistor 100 at different temperatures. FIG. 23 shows thesub-threshold swings in the diffusion area and the BTBT area extractedfrom FIG. 22 . It can be seen from FIG. 23 that in the diffusion area,the sub-threshold swing decreases with the decrease of temperature;while in the BTBT area, the sub-threshold swing does not change with thedecrease of temperature, which proves that the back-gate tunnelingtransistor 100 in the BTBT region works under the band-to-band tunnelingmechanism.

FIG. 24 shows a typical output curve of the CNT-MoS₂ heterostructure inthe back-gate tunneling transistor 100 under different gate voltages inthe BTBT operating mode, wherein the typical output curve is drawn on asemi-logarithmic scale. FIG. 25 shows an energy band view of a reverserectifier diode in reverse bias. FIG. 26 shows an energy band view of aZener diode under reverse bias. The working mechanisms of the reverserectifier diode and the Zener diode are both band-to-band tunneling(BTBT). The difference is that the reverse rectifier diode will have areverse current under a small reverse voltage; for the Zener diode, onlyafter the reverse voltage reaches a certain value, the reverse currentcan be turned on. FIG. 27 shows the temperature-dependent output curvesin the BTBT state when Vg=20V. FIG. 28 shows inverse slopes of theband-to-band tunneling current (BTBT current) versus temperature whenVg=20V. FIG. 29 shows a mapping diagram of the current Ids of the sourceelectrode 108 and the drain electrode 109 at a temperature of 130K. Itcan be seen from FIG. 29 that the shoulder peak and the main peak areclearly separated. FIGS. 24 to 29 are analysis of the outputcharacteristics of the BTBT area.

The fourth embodiment further provides a comparative experiment betweena metallic carbon nanotube field effect transistor (the middle portionof the metallic carbon nanotube is covered and in direct contact withthe MoS₂ film) and a pure metallic carbon nanotube field effecttransistor to verify that the MoS₂ film also performs n-type doping tothe metallic carbon nanotube. The only difference between the metalliccarbon nanotube field effect transistor and the back-gate tunnelingtransistor 100 is: in the metallic carbon nanotube field effecttransistor, the metallic carbon nanotube serves as the channel layer; inthe back-gate tunneling transistor 100, the semiconducting carbonnanotube serves as the channel layer. The only difference between thepure metallic carbon nanotube field effect transistor and the metalliccarbon nanotube field effect transistor is that in the pure metalliccarbon nanotube field effect transistor, the metallic carbon nanotubeserves as the channel layer and does not covered by the MoS₂ film and isnot in direct contact with the MoS₂ film; in the metallic carbonnanotube field effect transistor, one portion of the metallic carbonnanotube used as the channel layer, such as the middle portion of themetallic carbon nanotube, is covered by the MoS₂ film and is in directcontact with the MoS₂ film.

FIG. 30 shows transfer characteristic curves of the pure metallic carbonnanotube field effect transistor and the metallic carbon nanotube fieldeffect transistor having the MoS₂ film. In FIG. 30 , “mCNT” representsthe metallic carbon nanotube. It can be seen from FIG. 30 that an extraDirac point appears in the transfer characteristic curve of the metalliccarbon nanotube that is covered by the MoS₂ film and in direct contactwith the MoS₂ film, as indicated by the arrow of FIG. 30 , due toelectron doping to the portion of the metallic carbon nanotube being indirect contact with the MoS₂ film. It can be proved that the metalliccarbon nanotube is also doped n-type by the MoS₂ film, the portion ofthe metallic carbon nanotube that is in direct contact with the MoS₂film is changed from p-type doping to n-type doping, and the portion ofthe metallic carbon nanotube that is not in direct contact with the MoS₂film is still p-type.

Referring to FIG. 31 , a top-gate tunneling transistor 200 of a fifthembodiment is provided. The top-gate tunneling transistor 200 includesthe single carbon nanotube 12, the film-like structure 14, the sourceelectrode 108, the drain electrode 109, the insulating layer 106, andthe gate 104. The top-gate tunneling transistor 200 may be formed on asurface of the insulating substrate 102. The single carbon nanotube 12is a semiconducting carbon nanotube. In one embodiment, the top-gatetunneling transistor 200 consists of the single carbon nanotube 12, thefilm-like structure 14, the source electrode 108, the drain electrode109, the insulating layer 106, and the gate 104.

The single carbon nanotube 12 is located on the surface of theinsulating substrate 102, and the film-like structure 14 covers aportion of the single carbon nanotube 12 and is in direct contact withthe outer surface of this portion. Since the single carbon nanotube 12is one-dimensional and the film-like structure 14 is two-dimensional, aportion of the film-like structure 14 is in direct contact with aportion of the single carbon nanotube 12, and another portion of thefilm-like structure 14 is in direct contact with the insulatingsubstrate 102. The drain electrode 109 is electrically connected to thesingle carbon nanotube 12, and the source electrode 108 is electricallyconnected to the film-like structure 14. The insulating layer 106 coversthe source electrode 108, the film-like structure 14, the single carbonnanotube 12, and the drain electrode 109. The gate 104 is located on thesurface of the insulating layer 106 away from the insulating substrate102. The insulating layer 106 electrically insulates the sourceelectrode 108, the film-like structure 14, the single carbon nanotube12, and the drain electrode 109 from the gate 104.

It can be understood that, depending on the specific forming process,the insulating layer 106 does not need to completely cover the sourceelectrode 108, the film-like structure 14, the single carbon nanotube12, and the drain electrode 109, as long as it can be ensured that thegate electrode 104 is insulated from each of the source electrode 108,the film-like structure 14, the single carbon nanotube 12, and the drainelectrode 109.

The top-gate tunneling transistor 200 in the fifth embodiment is similarto the back-gate tunneling transistor 100 in the fourth embodiment,except that the former is a top-gate type, and the latter is a back-gatetype. The structures, materials and dimensions of the single carbonnanotube 12, the film-like structure 14, the source electrode 108, thedrain electrode 109, the insulating layer 106, and the gate 104 in thefifth embodiment are the same as those in the fourth embodiment.

The back-gate tunneling transistor 100 in the fourth embodiment and thetop-gate tunneling transistor 200 in the fifth embodiment have thefollowing advantages: first, the single semiconducting carbon nanotubecontains p-type and n-type, and electrons can be tunneled from p-typedoping to n-type doping to achieve band to band tunneling (BTBT);second, one-dimensional single semiconducting carbon nanotube andtwo-dimensional MoS₂ film (or WS₂ film) combine to have excellentcontrollability of the gate 104; third, the ideal interface with strongcoupling between the unique single semiconducting carbon nanotube andthe two-dimensional MoS₂ film (or WS₂ film) can increase the on-currentand reduce the sub-threshold swing; fourth, since the surface of theinsulating layer 106 is the atomic level flat surface without danglingbonds, so that the insulating layer 106 can shield the charge dopingfrom the surface of the gate 104.

Referring to FIG. 32 , a method of p-type doping carbon nanotubes in asixth embodiment is provided, and the method includes the followingsteps:

S61, providing a single carbon nanotube 12;

S62, providing a layered structure 16, wherein the layered structure 16is a tungsten diselenide (WSe₂) film or a black phosphorus (BP) film;and

S63, making the layered structure 16 in direct contact with at least oneportion of the single carbon nanotube 12.

During step S62, the tungsten diselenide (WSe₂) film or the blackphosphorus (BP) film is a two-dimensional film. The material of the WSe₂film is WSe₂, and the material of the black phosphorus film is blackphosphorus.

During step S63, the single carbon nanotube 12 may be completely coveredby the layered structure 16 or partly covered by the layered structure16. The layered structure 16 can cover and be in direct contact with aportion of the single carbon nanotube 12, while another portion of thesingle carbon nanotube 12 is exposed and is not in direct contact withthe layered structure 16. The layered structure 16 can also cover and bein direct contact with the entire single carbon nanotube 12. All thecarbon nanotubes covered by the layered structure 16 are in directcontact with the layered structure 16. As shown in FIG. 33 , the layeredstructure 16 covers and is in direct contact a portion of the singlecarbon nanotube 12. As shown in FIG. 34 , the layered structure 16covers and is in direct contact the entire upper surface of the singlecarbon nanotube 12.

The portion of the single carbon nanotube 12 that is in direct contactwith the layered structure 16 is defined as the contact portion, and thepart of the single carbon nanotube 12 that is not in direct contact withthe layered structure 16 is defined as the exposed portion. The singlecarbon nanotube 12 can consist of the contact portion and the exposedportion.

The carbon nanotube itself is p-type, but in practical applications, itis still necessary to p-doping to carbon nanotube that is p-type. Thelayered structure 16 is in direct contact the contact portion, WSe₂ orblack phosphorus contributes holes to the contact portion, and holesenter the contact portion from WSe₂ or black phosphorus, so that thecontact portion is p-doped. In one embodiment, holes only enter thecontact portion from WSe₂ or black phosphorus, so that only contactportion is p-type doped by covering the contact portion with the layeredstructure 16, and the exposed portion is not p-type doped by coveringthe contact portion with the layered structure 16. At this time, theexposed portion of the single carbon nanotube 12 is still p-type,because the carbon nanotube itself is p-type. The entire single carbonnanotube 12 is p-type.

The method of p-type doping the carbon nanotube in the sixth embodimentis similar to the method of n-type doping the carbon nanotube in thefirst embodiment except that: in the first embodiment, the film-likestructure 14 covers and is in direct contact with at least one portionof the carbon nanotube 12, and the material of the film-like structure14 is molybdenum disulfide or tungsten disulfide, so that the at leastone portion of the carbon nanotubes covered by the film-like structure14 is n-type doped, which is changed from p-type doping to n-typedoping, and the at least one portion of the single carbon nanotube 12 isn-type; in the sixth embodiment, the layered structure 16 covers and isin direct contact with at least one portion of the single carbonnanotube 12, and the material of the layered structure 16 is tungstendiselenide or black phosphorus, so that the at least one portion of thecarbon nanotubes covered by the layered structure 16 is p-type doped,and the single carbon nanotube 12 is p-type as a whole. The type andsize of the single carbon nanotube 12 and the size of the layeredstructure 16 in the sixth embodiment are the same as the type and sizeof the single carbon nanotube 12 and the size of the film-like structure14 in the first embodiment.

The sixth embodiment further provides a comparative experiment between acarbon nanotube field effect transistor having a WSe₂ film and a purecarbon nanotube field effect transistor without having the WSe₂ film toverify that the WSe₂ film can p-type dope to the carbon nanotube. Theonly difference between the pure carbon nanotube field effect transistorand the carbon nanotube field effect transistor having the WSe₂ film is:the pure carbon nanotube field effect transistor does not include theWSe₂ film, and the carbon nanotube of the pure carbon nanotube fieldeffect transistor is not covered by the WSe₂ film and is not in directcontact with the WSe₂ film; in the carbon nanotube field effecttransistor having the WSe₂ film, a portion of the carbon nanotube iscovered by the WSe₂ film and is in direct contact with the WSe₂ film.

FIG. 35 shows transfer characteristic curves of the carbon nanotubefield effect transistor having the WSe₂ film and the pure carbonnanotube field effect transistor without having the WSe₂ film. It can beseen from FIG. 35 that the carbon nanotube field effect transistorhaving the WSe₂ film and the pure carbon nanotube field effecttransistor without having the WSe₂ film have a common switch off pointat ˜−18V, and the transfer characteristic curve of the carbon nanotubefield effect transistor having the WSe₂ film has an additional switchoff point near +5V, which proves that the doping levels of thesemiconducting carbon nanotubes covered by WSe₂ film and thesemiconducting carbon nanotubes not covered by WSe₂ film are different.

Before the single carbon nanotube is in direct contact with the WSe₂film, the single carbon nanotube is a one-dimensional bipolar channeldominated by p-type, and the WSe₂ film is a two-dimensional p-typechannel. After the single carbon nanotube is in direct contact with theWSe₂ film, holes spontaneously transfer from the WSe₂ film to theportion of the semiconducting carbon nanotube that is covered by theWSe₂ film and is in direct contact with the WSe₂ film. Therefore, whenthe portion of the carbon nanotube not covered by WSe₂ film changes fromp-type doping to n-type doping under the adjustment of the gate voltage,the carbon nanotube covered by WSe₂ film still remains p-type. When theholes in WSe₂ film are depleted, the portion of carbon nanotube coveredby WSe₂ film changes from p-type doping to n-type doping, to form asecond switch off point. It can be proved that the portion of the carbonnanotube that is covered by the WSe₂ film and is in direct contact withthe WSe₂ film is P-type doped, and the portion of the carbon nanotubethat is not covered by the WSe₂ film and is not in direct contact withthe WSe₂ film is not P-type doped.

Referring to FIG. 36 , a method of p-type doping carbon nanotubes in aseventh embodiment is provided, and the method includes the followingsteps:

S71, providing a plurality of single carbon nanotubes 12 spaced apartfrom each other;

S72, providing the layered structure 16, and the layered structure 16 isthe tungsten diselenide (WSe₂) film or the black phosphorus (BP) film;and

S73, covering the plurality of single carbon nanotubes 12 with thelayered structure 16, wherein at least one portion of each of theplurality of single carbon nanotubes 12 is in direct contact with thelayered structure 16.

The method of p-type doping carbon nanotubes in the seventh embodimentis similar to the method of p-type doping the carbon nanotube in thesixth embodiment, except that: in the sixth embodiment, the tungstendiselenide (WSe₂) Film or the black phosphorous (BP) film covers atleast one portion of one single carbon nanotube 12; in the seventhembodiment, the tungsten diselenide (WSe₂) film or the black phosphorous(BP) film simultaneously covers at least one portion of each of theplurality of carbon nanotubes 12.

During step S71, in one embodiment, the length extending directions ofthe plurality of single carbon nanotubes 12 are parallel to each other.

During step S73, the tungsten diselenide (WSe₂) film or the blackphosphorus (BP) film can simultaneously cover a portion of each of theplurality of single carbon nanotubes 12, so that a portion of eachsingle carbon nanotube 12 is p-type Doped. The tungsten diselenide(WSe₂) film or the black phosphorus (BP) film can cover an entirety ofthe multiple single carbon nanotubes 12, so that an entirety of eachsingle carbon nanotube 12 is fully p-type doped.

The methods for p-type doping carbon nanotubes in the sixth and seventhembodiments have the following advantages: first, the tungstendiselenide (WSe₂) film or the black phosphorus (BP) film is in directcontact at least one portion of a single carbon nanotube 12, so that theat least one portion of the single carbon nanotube 12 can be p-doped;second, the tungsten diselenide (WSe₂) film or the black phosphorus (BP)film can cover an entirety of the multiple single carbon nanotubes 12,so that the multiple single carbon nanotubes 12 can be p-doped at thesame time; third, the method is simple, and the p-type doping effect isgood.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the disclosure. Any elements describedin accordance with any embodiments is understood that they can be usedin addition or substituted in other embodiments. Embodiments can also beused together. Variations may be made to the embodiments withoutdeparting from the spirit of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method of n-type doping a carbon nanotube,comprising: providing a single carbon nanotube: providing a film-likestructure, wherein the film-like structure is a molybdenum disulfidefilm or a tungsten disulfide film; and converting at least one portionof the carbon nanotube from a p-type doping to an n-type doping bycovering the carbon nanotube with the film-like structure.
 2. The methodof claim 1, wherein a material of the molybdenum disulfide film ismolybdenum disulfide, and a material of the tungsten disulfide film istungsten disulfide.
 3. The method of claim 1, wherein the carbonnanotube is a single-walled carbon nanotube or a double-walled carbonnanotube.
 4. The method of claim 1, wherein one portion of the carbonnanotube that is in direct contact with the film-like structure isdefined as a contact portion, and the contact portion is changed fromp-type doping to n-type doping.
 5. The method of claim 1, wherein oneportion of the carbon nanotube that is in direct contact with thefilm-like structure is changed from p-type doping to n-type doping, andthe other portion of the carbon nanotube that is not in direct contactwith the film-like structure is p-type.
 6. The method of claim 1,wherein an entirety of the carbon nanotube is in direct contact with thefilm-like structure, so that the entirety of the carbon nanotube ischanged from p-type doping to n-type doping.
 7. The method of claim 1,wherein controlling an amount of n-type doping of the carbon nanotube byadjusting a portion of the carbon nanotube which is covered with thefilm-like structure.
 8. A method of n-type doping a carbon nanotube,comprising: providing a plurality of carbon nanotubes spaced apart fromeach other; providing a film-like structure, wherein the film-likestructure is a molybdenum disulfide film or a tungsten disulfide film,and covering the plurality of carbon nanotubes with the film-likestructure, wherein the plurality of carbon nanotubes is in directcontact with the film-like structure.
 9. The method of claim 8, whereinlength extending directions of the plurality of carbon nanotubes areparallel to each other.
 10. The method of claim 8, wherein at least oneportion of each of the plurality of carbon nanotubes is in directcontact with the film-like structure.
 11. The method of claim 8, whereina material of the molybdenum disulfide film is molybdenum disulfide, anda material of the tungsten disulfide film is tungsten disulfide.
 12. Themethod of claim 8, wherein at least one portion of each of the pluralityof the carbon nanotubes that is in direct contact with the film-likestructure is changed from p-type doping to n-type doping.
 13. The methodof claim 12, wherein one portion of the plurality of carbon nanotubesthat is not in direct contact with the film-like structure is p-type.14. The method of claim 8, wherein an entirety of the plurality ofcarbon nanotubes is in direct contact with the film-like structure, sothat an entirety of each of the plurality of carbon nanotubes is changedfrom p-type doping to n-type doping.
 15. A method of n-type doping acarbon nanotube, comprising: providing a plurality of carbon nanotubesspaced apart from each other; providing a film-like structure, whereinthe film-like structure is a molybdenum disulfide film or a tungstendisulfide film; and covering the plurality of carbon nanotubes with thefilm-like structure.
 16. The method of claim 15, wherein lengthextending directions of the plurality of carbon nanotubes are parallelto each other.
 17. The method of claim 15, wherein one portion of eachof the plurality of carbon nanotubes is in direct contact with thefilm-like structure, and the other portion of each of the plurality ofcarbon nanotubes is not in direct contact with the film-like structure.18. The method of claim 15, wherein a material of the molybdenumdisulfide film is molybdenum disulfide, and a material of the tungstendisulfide film is tungsten disulfide.
 19. The method of claim 15,wherein controlling an amount of n-type doping of the plurality ofcarbon nanotubes by adjusting a portion of the plurality of carbonnanotubes which is covered with the film-like structure.